Cellular technologies, such as GERAN (GSM EDGE radio access network), UTRAN (UMTS terrestrial radio access network), LTE (Long Term Evolution), Wi-Fi, etc., require spectrum resources as basic means of data and voice communication. Spectrum is fundamental to the success of wireless communications and mobile operators rely on exclusive licenses as a key asset for ensuring predictable service.
The range of spectrum that is made available for wireless communications has increased over years, but despite this increase the demand for new spectrum still exceeds the available exclusive spectrum. The scarcity of spectrum has created a need for techniques for assigning spectrum resources, which allows sharing licensed spectrum with other operations or applications.
One framework to address the sharing of spectrum is Licensed Sharing Access (LSA), also sometimes referred to as Authorized Shared Access (ASA) or Spectrum Access System (SAS). Within this framework, it would be feasible for an operator or other licensee to use spectrum that is partly utilized already by other applications.
A basic framework to handle the sharing of spectrum and to avoid interference between applications has been defined by the Internet Engineering Task Force (IETF) as a Protocol to Access White-Space Databases (PAWS). The framework of LSA extends beyond the capabilities defined in the IETF PAWS.
Standardization of an LSA framework and related interfaces is ongoing in the European Telecommunications Standards Institute (ETSI) as a Reconfigurable Radio Systems (RRS). In parallel, the Federal Communications Commission (FCC) in the USA is defining a regulatory framework for use of spectrum at 3.5 GHz as a step in the President's Council of Advisors on Science and Technology (PCAST) recommendations to identify 1000 MHz of federal spectral resources to create shared-use spectrum superhighways.
In the framework defined by the FCC, the use of SAS is required. The SAS is not only required to ensure that licensees use the correct set of spectrum resources, e.g. in terms of frequency, geographical and timing domain. The SAS is also required to monitor the utilization of the spectrum resources by licensees.